The invention relates to a conveying and separating device for root crop comprising a separating stretch receiving a harvested mixture of potatoes, beets, or similar root crop and rocks, clods of soil or like admixed parts, wherein the separating stretch has at least two rotatingly driven separating rollers on which, on the topside, primarily the root crop is conveyed while the admixed parts are removed in a screening phase by means of a screening gap between the separating rollers. The invention further relates to a method for separating root crop, e.g. potatoes or beets, from a harvested mixture with rocks, clods of soil, dirt, and like admixed parts, wherein the mixture is placed onto a separating stretch comprised of at least two rotatingly driven separating rollers, the admixed parts are removed in a screening phase by means of a screening gap between the separating rollers and the root crop is conveyed on the topside of the separating rollers.
Such screening and conveying devices have been known for a long time in agricultural engineering. According to DD 36 677 (1963) a device with two roller tables is provided wherein the rollers have disk-like conveying elements that are arranged staggered to one another and in the screening gap mesh with one another. In a screening and separating device according to DE 19 46 207 (1966), the interacting meshing roller bodies have elliptical disks as conveying elements so that the conveying action can be increased while the separation or screening effect is improved. DE 22 05 309 (1972) and DE 22 39 783 (1972) propose a root crop cleaning device in which two drums rotating in the same direction are provided with oppositely oriented helical guiding ribs; the devices provide improved pulling apart of the harvested mixture as well as a more intensive movement of the crop so that the separation of soil clods and the like admixed parts is improved.
In a potato harvesting machine according to DE 23 12 111 C2 (1974) in the area of two screen conveyor belts a single roller provided with helical projections is arranged with which an improvement of the separating effect in the conveying gap between the two screen conveyor belts is achieved.
According to DE 26 51 206 (1976) a device for cleaning root crop is proposed in which the mixture is fed into the area between two rotating cleaning rollers. These cleaning rollers can be moved as needed in the axial direction and radial direction by appropriate drive means. For removing soil layers adhering to the rollers, a plate-shaped or finger-shaped stripping device is provided that has an additional drive mechanism.
According to DE 28 11 611 C3 (1978) a soil removing device for root crop is proposed in which the separating members are embodied in the form of disk rollers, similar to the devices of DD 36 677 and DE 19 46 207, so that the disks are meshing with one another and are positioned staggered so as to centrally engage the gaps between two neighboring disks of a roller. In addition to the conveying and separating movement, removal of soil from the intermediate spaces is to be achieved by disks that are arranged as tumbling tools. This system is based on a geometric concept that is however impractical. The tumbling disks that are arranged at a slant to the longitudinal axis of the rollers act as adhesion bodies already when the soil that is applied has only a minimal moisture content because soil contacting the tumbling disks causes a cylindrical filling of the open shape so that the entire cleaning stretch will clog and the cleaning effect is extremely reduced; already after a short period of time blockage of the entire system may result.
In a rotational separator according to G 81 16 786.5 (1981) that is also similarly impractical there is also a cleaning action provided for the gaps between the disks of the rotational separator wherein disks each have thicker portions with which areas of the downstream disks or gaps between the disks are to be kept free of deposits. Similar to these thicker portions acting as stripping devices, DD 214 108 (1983) proposes a roller pair provided with a stripping device that engages between the roller pair (similar to the arrangement of DE 26 51 206) is used for cleaning the rollers.
DE 36 36 668 C2 (1986) discloses a method and an arrangement for conveying and cleaning beets wherein the cleaning stretch is also provided with staggered disks mounted on roller bodies, respectively. Cleaning of the system or of the crop is realized in that the crop is repeatedly thrown in the air along the conveying stretch and, in this way, the crop is separated from the admixed parts that reach a minimal height in comparison to the crop. In the area of the meshing disks, soil, haulm, and the like can deposit on the surface of the disks so that the screening action is disadvantageously reduced and complex cleaning phases are required.
According to DE 298 03 880 U1 (1998) a conveying and separating device has roller bodies provided with star wheels wherein these star wheels have fingers with different deformation or displacement capabilities for improving the conveying and separating function. This construction, similar to DE 23 12 111 C2, is provided for separating haulm wherein a haulm picking roller is arranged in the passage between a deflection roller and a screen conveyor belt and blockage of the system is prevented. DE 199 47 484 A1 (1999) discloses a harvesting machine provided with a haulm separating device with several conveying rollers that are moveable in a direction parallel to their axis and between which a variable gap is adjustable in order to match the screening and conveying output to the soil conditions, respectively.
According to DE 299 15 450 U1 (1999) a separating and transfer roller for root crop, in particular potatoes, is proposed wherein the roller has a jacket that is made of resilient material and is designed to yield toward the interior of the roller body. In this way, an elastic system is utilized with which deposition of sticky soil is prevented because the cleaning action is achieved by the roller jacket that carries out a strong kneading action.
In addition to the aforementioned plurality of stripper constructions that require additional components, control-technological solutions in regard to driving the rollers have been proposed also for cleaning the rollers. In particular, after interruption of the mixture feed to the rollers, the rollers can be moved at increased rotary speed so fast that cleaning by centrifugal force of the roller surface is achieved. These cleaning processes require additional protective devices, the productivity of the device is disadvantageously reduced because of the downtimes for cleaning the system, and complete removal from the system of fiber material admixed with sticky soil is not achievable.
The object of the present invention is to provide a method for separating root crop from a mixture as well as a conveying and separating device for carrying out this method, wherein the method and the device should be useable without causing blockage even in connection with admixtures that are comparatively moist and have the tendency to stick to the crop so that downtimes for additional cleaning phases are prevented and an increase of productivity of the agricultural separating process is enabled.